CSMA,althoughmoreefficientthanALOHAorslottedALOHA,stillhasoneglaringinefficiency.Ifthemediumisbusy,thestationwillwaitforarandomamountoftime.Whentwoframescollide,themediumremains(请作答此空)forthedurationoftransmissionofbothdamagedframes.Theuseofrandomdelaysreducestheprobabilityof().For()frames,comparedtopropagationtime,theamountofwastedcapacitycanbeconsiderable.Thiswastecanbereducedifastationcontinuestolistentothemediumwhile().Themaximumutilizationdependsonthelengthoftheframeandonthe()time;thelongertheframesortheshorterthepropagationtime，thehighertheutilization.
A.convenient B.inconvenient C.usable D.unusable正确答案D
